As known, many inorganic salts and oxides, among them components of mixed fertilizers like potassium chloride and the nitrogenous salts (ammonium nitrate, ammonium sulfate, sodium nitrate and diammonium phosphate) are hygroscopic and therefore cake or coalesce when stored, particularly at elevated humidity, temperature and pressure. Materials of this type are not suitable for storage in bulk since after such storage they cannot be spread readily by mechanical spreaders.
In order to reduce caking, hygroscopic materials of this type (including fertilizers) are produced in the form of pellets or "prills" of equal size which are coated with talcum, kieselguhr, diatomaceous earth or chalk in order to prevent absorption of moisture. But in these methods large amounts of one or more of these anti-caking agents must be added, so that when the material is a fertilizer its nutrient content is reduced and in any event considerable dust is developed when the coated particles are spread.
U.S. Pat. No. 2,480,694 discloses that fatty amines and their derivatives prevent the caking of fertilizers. Solutions of fatty amines in mineral oil and the spraying of these solutions on fertilizers are described in U.S. Pat. No. 3,186,828. In general, fatty amines (including fatty diamines) which contain a fatty radical of 8 to 22 carbon atoms, as well as their salts (particularly the acetates and chlorides) and their ethoxylates, are used. But these methods and products have the disadvantage that the anticaking effect achieved with fatty amines and their derivatives is not satisfactory. It is difficult to apply the solid fatty amines evenly to the salt or fertilizer material; and the products are not harmless because of their strong amine odor and their tendency to irritate the eyes and skin.